Method and apparatus for checking firing pressure of ammunition

ABSTRACT

A method and an apparatus are described for enabling a sportsman to determine the correct amount of powder that he should add to firearm cartridges to produce maximum safe working pressures. A shallow cavity is formed in the sidewall of the cartridge. A calibrated thin metal disc is seated in the cavity with the outer surface of the disc flush with the cartridge wall. The disc has a recessed center section with reduced thickness that is calibrated to deform or bulge outward to make contact with the firing chamber wall when the maximum safe working pressure is exerted on the interior of the cartridge.

I United States Patent 1 3,568,600 7 Inventor John A31 3,345,876 10/1967Smith 73/167X B d O 3,443,430 5/1969 York etal 73/167 [21] App]. No.751,286 OTHER REFERENCES 1 Flled Aug-8,1968 Internal Ballistic,published 1951, copy in NY [45] patmed 1971 Philosophical Library; pp.112. [731 Asslgnee Robe" Amos SMOKELESS SHOTGUN POWDERS; 1935; byWallace Gales Ferry Conn H. Cox; pub. E. I. duPont NeMours 81: Co., Inc.pp. 73 & 74

' Primary Examiner-Robert F. Stahl [54] METHOD AND APPARATUS FORCHECKING Attorney-Wells & St. John FIRING PRESSURE 0F AMMUNITION 9Claims, 6 Drawing Figs.

- ABSTRACT: A method and an apparatus are described for U-S. bli g asportsman t d t i th correct amount f 73/167 86/23 powder that he shouldadd to firearm cartridges to produce [51 1 llltmaximum safe workingpressures A shallow cavity is fomed [50] Field of 73/167, in thesidewall f the cartridge A calibrated thin meta] disc is (lnqmred);10238143151; 86/1, 20,23 31 seated in the cavity with the outer surfaceof the disc flush with the cartrid e wall. The disc has a recessedcenter section [56] References Cited with reduced th ickness that iscalibrated to deform or bulge UNITED STATES PATENTS outward to makecontact with the firing chamber wall when 1,062,604 5/1913 Pedersen102/43 the maximum safe working pressure is exerted on the interior1,123,362 1/1915 Pedersen... 102/43 ofthe cartridge.

Patented March 9, 1971 3,568,600

INVENTOR.

151m A. Nos/m 7/424? .QZV

Avg s.

METHOD AND AFPPTHJS FOR CHIECG mo PRESSURE Oh AMMUNTTION BACKGROUND OFTHE INVENTION This invention relates to methods and apparatus for determining the correct amount of powder that should be loaded into firearmcartridges to produce safe firing pressures.

has always been difiicult for sportsmen who are interested in reloadingspent firearm cartridges to accurately determine the maximum amount ofpowder that should be loaded in the cartridges to produce efficienttiring pressures without exceeding the safe limit of the cartridge. Itis well known that the type of the primer, the type and size of thecartridge, the style of the bullet and the particular powder lot are allimportant factors that bear on the amount of the powder that should beadded to provide efficient and safe working pressures. One combinationmay produce a safe load while another combination may produce adangerous load. Many accidents have occurred because the sportsman wasunable to determine the correct amount of powder to reload spentcartridges.

One of the objects of this invention is to provide a method andapparatus for determining the correct amount of powder that should beloaded in spent cartridges upon reloading.

An additional object of this invention is to provide such an apparatusand method that may be readily used by sportsmen without requiringelaborate and expensive test equipment.

A further object of this invention is to provide a pressure indicatorfor mounting to the side of the cartridge for measuring the explosivepressure on the interior of the cartridge during firing without havingto puncture the wall of the cartridge.

An additional object of thisinvention is to provide a deformable objectthat may be seated in the wall of a cartridge for generating anindication of the magnitude of the pressure on the inside of thecartridge during firing.

A still further object of this invention is to provide a small disc thatmay be inserted between the cartridge case and the tiring chamber of thefirearm to gauge the pressure during firing.

These and other objects and advantages of this invention will becomeapparent upon the reading of the following detailed description of apreferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of thisinvention is illustrated in the accompanying drawings, in which:

FlG. l is a plan view of a test cartridge incorporating the principlefeatures of this invention particularly emphasizing the placement of athin metal disc in the side of the cartridge;

hi6. 2 is a plan view of the thin metal disc;

FIG. 3 is a side elevational view of the thin metal disc;

FlG. d is a side elevation of the thin metal disc showing the thin metaldisc formed to complement the curvature of the wall of the cartridge;

FIG. 5 is a schematic cross-sectional view showing the test cartridge,with a bullet mounting therein, positioned in a firing chamber prior todetonation; and

Fit}. 65 is a fragmentary schematic view similar to FIG. 5 exceptshowing the cartridge after it has been detonated emphasizing thedeformation of the thin metal disc.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1there is shown a test cartridge that has a forward neck section 13 forreceiving a bullet and a flared shoulder section l2 extending to atubular wall 13. The rear end of the cartridge is enclosed by the basei4 containing a primer.

The test cartridge has a pressure indicator for gauging the interiorpressure during tiring. The pressure indicator includes a localized wallsegment in with a deformable portion 17 that is recessed inwardly fromthe outer surface of the tubular wall.

The deformable portion 17 has a thickness less than the surroundingportion of the wall segment 116. The deformable portion 17 is calibratedto deform a prescribed amount when the interior pressure on thecartridge approaches the maximum safe limit of the cartridge.

As shown in the drawings, the localized wall section includes twoelements or thicknesses-an indented wall member l? and a thin disc 20.The indented wall member 18 is a continuous segment of the cartridgewall that has been indented a prescribed amount to form a circularcavity 19 for receiving the disc 20. The disc 20 is made from a mildsteel. The disc 20 is seated in the cavity l9 so that the outer surface21 of the disc is flush with and conforms with the outer surface of thetubular wall 13. The disc 20 has a deformable circular center section22. The circular center section 22 is recessed a predetermined distanceso that the amount of subsequent bulge or deformation will be indicativeof the interior firing pressure exerted on the cartridge. The disc 20has an inner surface 23 with beveled edges so that. when the disc isseated in the cavity 19 it will not puncture the wall member 18 of thecartridge. Initially the disc is formed as shown in FIG. 2 and 3 withthe circular center section having a flat-bottomed recess. The disc 20is then curved as shown in FIG. 4 to conform to the curvature of thetubular wall 13 so that when the disc is seated in the indentation 19the outer surface 21 of the disc 20 will be flush with the outer surfaceof the tubular wall 13.

To determine the correct amount of powder that should be added to thecartridge to provide a maximum safe firing or working pressure for aparticular type cartridge, a test cartridge 10 is initially loaded withan amount of powder believed to be less than the amount that willproduce the maximum safe pressure. A bullet 25 is then mounted in theneck portion of the cartridge. The cartridge 10 with the bullet isloaded in a firing chamber 26 having an interior wall 27 that conformsto the outer surface of the cartridge as shown in FIG. 5. If the amountof powder added to the cartridge is less than that which will producethe maximum safe working pressure, then the deformable portion 17 whichincludes the circular center section 22 of the disc will only partiallybulge without engaging the inner wall 27 of the firing chamber 26.

Additional amounts of powder are added to the cartridge l0 until thedeformable portion l7 will bulge outwardly to make contact with theinterior surface 27 of the firing chamber to form a small flat segmenton the bulge. When the cartridge is removed from the firing chamber, thesmall flat segment may be readily visually observed indicating that thecorrect amount of powder was added to the cartridge.

If an excess amount of powder is added to the cartridge the deformableportion 17 will deform to such a point that a very large flat area willbe formed on the bulge.

Through a trial and error method, by successful loading and detonatinggradually increasing amounts of powder in the car tridge, one canvisually determine when the correct amount of powder has been added tothe cartridge.

It is desirable that the discs 20 be as small in diameter and as thin aspossible in order to not displace any more of the combustion volume ofthe cartridge than is necessary. It has been found that a disc ofapproximately five-sixteenths of an inch in diameter and having athickness of 0.035 in. is particularly suitable for medium to largecartridges. The circular center section is initially formed with aVs-inch-diameter indentation that is 0.015 in. deep having a flatbottom.

It is also important that the wall segment 16 be located in an area ofthe tubular wall that has a uniform thickness in strength.

if a sportsman desires to determine the correct amount of powder to beadded to a particular type and model of cartridge, he first determinesthe maximum safe working pressure of the cartridge. This information isreadily available from the manufacturer. The sportsman then purchasesdiscs 20 that are calibrated for that particular working pressure. Forexample, if a particular type of cartridge has a maximum safe firingrating of 40,000 psi. then the sportsman will purchase discs that arecalibrated for 40,000 p.s.i. The sportsman makes a cavity 19 in a spentcartridge. The disc is seated in the cavity to form r test cartridge.The sportsman then starts out with a reduced load and works up a grainor two at a time during each loading and firing until the bulge of thecircular center 22 makes contact with the interior wall of the firingchamber 26. He will then know that the components he is using in thisparticular rifle or firearm are within the safe limits of the 40,000psi. category.

It should be understood that the above described embodiment is simplyillustrative of the principles of this invention and that numerous otherembodiments or modifications may be readily devised without deviatingfrom the principles thereof. Therefore, only the following claims areintended to define this invention.

I claim:

1. A test cartridge for determining the correct amount of powder thatshould be loaded in selected cartridges to produce a safe firingpressure, said test cartridge comprising:

a cartridge having a tubular wall with a wall section which has adeformable portion thereof that is recessed inward so that when the testcartridge is subjected to said safe firing pressure the deformableportion will deform outward a predetermined amount; and

the wall section including a thin metal disc that is seated in the sideof the tubular wall without puncturing the tubular wall, said dischaving a recessed center section with a reduced thickness.

2. A test cartridge as defined in claim 1 wherein the disc is producedfrom uniform mild steel.

' 3. A test cartridge as defined in claim 1 wherein the disc is seatedin the tubular wall so that the outer surface of the disc is flush withthe outer surface of the tubular wall.

4. A test cartridge as defined in claim 1 wherein the disc has athickness of approximately 0.035 in. and the center section is recessedapproximately 0.015 in. v

5. A pressure indicator for mounting to the sidewall of a firearmcartridge to determine the correct amount of powder to be loaded in thecartridge to produce a safe firing pressure, said pressure indicatorcomprising a thin metal disc seated in the sidewall of the cartridgeflush with the outer surface of the sidewall, said thin metal dischaving a deformable center section with a reduced thickness that willdeform a predetermined distance when the cartridge is subjected to theselected safe firing pressure.

6. A pressure indicator as defined in claim 5 wherein the deformablecenter section of the disc is recessed below the outer surface of thecartridge sidewall a distance equal to the predetermined distance sothat the central section will deform when subjected to the safe firingpressure.

7. A method of determining the correct amount of powder that should beloaded into tubular walled firearm cartridges to produce a safe firingpressure, said method comprising the steps of:

a. seating a test element in the exterior of the cartridge wallconforming with the exterior shape of the wall in which the test elementhas a deformable section that is recessed inwardly a predetermineddistance so that when the safe firing pressure is exerted on theinterior of the cartridge the deformable section will deform outwardlythe predetermined distance; and

b. successively loading and detonating gradually increasing amounts ofpowder in the cartridge until it can be visually observed that therecessed section has deformed outwardly the predetermined distance.

8. A method as defined in claim 7 wherein a shallow cavity is firstformed in the cartridge wall to receive the test element which is a thinmetal disc having a recessed center section with a reduced thicknessthat is calibrated to deform the predetermined distance when the safefiring pressure is exerted'on the interior of the cartridge.

9. A method as defined in claim 8 wherein the cartridge is positioned ina firing chamber for detonating so that when the safe firing pressure isexerted on the interior of the cartridge the recessed section willdeform outwardly making contact with the firing chamber.

1. A test cartridge for determining the correct amount of powder thatshould be loaded in selected cartridges to produce a safe firingpressure, said test cartridge comprising: a cartridge having a tubularwall with a wall section which has a deformable portion thereof that isrecessed inward so that when the test cartridge is subjected to saidsafe firing pressure the deformable portion will deform outward apredetermined amount; and the wall section including a thin metal discthat is seated in the side of the tubular wall without puncturing thetubular wall, said disc having a recessed center section with a reducedthickness.
 2. A test cartridge as defined in claim 1 wherein the disc isproduced from uniform mild steel.
 3. A test cartridge as defined inclaim 1 wherein the disc is seated in the tubular wall so that the outersurface of the disc is flush with the outer surface of the tubular wall.4. A test cartridge as defined in claim 1 wherein the disc has athickness of approximately 0.035 in. and the center section is recessedapproximately 0.015 in.
 5. A pressure indicator for mounting to thesidewall of a firearm cartridge to determine the correct amount ofpowder to be loaded in the cartridge to produce a safe firing pressure,said pressure indicator comprising a thin metal disc seated in thesidewall of the cartridge flush with the outer surface of the sidewall,said thin metal disc having a deformable center section with a reducedthickness that will deform a predetermined distance when the cartridgeis subjected to the selected safe firing pressure.
 6. A pressureindicator as defined in claim 5 wherein the deFormable center section ofthe disc is recessed below the outer surface of the cartridge sidewall adistance equal to the predetermined distance so that the central sectionwill deform when subjected to the safe firing pressure.
 7. A method ofdetermining the correct amount of powder that should be loaded intotubular walled firearm cartridges to produce a safe firing pressure,said method comprising the steps of: a. seating a test element in theexterior of the cartridge wall conforming with the exterior shape of thewall in which the test element has a deformable section that is recessedinwardly a predetermined distance so that when the safe firing pressureis exerted on the interior of the cartridge the deformable section willdeform outwardly the predetermined distance; and b. successively loadingand detonating gradually increasing amounts of powder in the cartridgeuntil it can be visually observed that the recessed section has deformedoutwardly the predetermined distance.
 8. A method as defined in claim 7wherein a shallow cavity is first formed in the cartridge wall toreceive the test element which is a thin metal disc having a recessedcenter section with a reduced thickness that is calibrated to deform thepredetermined distance when the safe firing pressure is exerted on theinterior of the cartridge.
 9. A method as defined in claim 8 wherein thecartridge is positioned in a firing chamber for detonating so that whenthe safe firing pressure is exerted on the interior of the cartridge therecessed section will deform outwardly making contact with the firingchamber.